Most state-of-the-art program controlled Private Branch Exchanges (PBX) have particular programs stored in the PBX memory for routing calls dialed by a PBX user which calls extend beyond the PBX. For example, the Dimension.RTM. PBX, designed by Bell Telephone Laboratories, Inc., and manufactured by the Western Electric Co., Inc. of New York, N.Y., has an Automatic Route Selection (ARS) and an Automatic Routing (AAR) programs stored within the PBX memory which programs examine the digits dialed by a PBX user to determine if the dialed digits describe a call placed beyond the PBX. If the programs determine that the dialed call extends beyond the PBX, the dialed digits are further examined to determine the most desirable (least expensive) communication route which can be established to complete the call. For instance, the programs will initially attempt to complete the call on leased facilities, such as outgoing trunks which are dedicated to the PBX customer's use (e.g., WATS, customer switching network). The PBX customer is charged a flat monthly rate for use of leased facilities as compared with charges paid per call for use of trunks associated with the Direct-Distance-Dialing (DDD) network. Additionally, since DDD charges vary with use during peak load periods at specific time intervals during the work day, use of leased facilities during these time periods result in uniform, and less expensive, billing.
Only after it is determined that the least expensive facilities are busy, will the PBX programs instruct the PBX system to attempt to place the call on an idle Direct-Distance-Dialing (DDD) network trunk. However, prior to establishing the call on the idle DDD trunk, the PBX system is instructed to transmit a one second distinctive tone to the calling user as a warning that the PBX system has selected an idle DDD trunk. If the user hangs up, the call is terminated before the DDD facilities are used and the user can attempt to place the call at a later time when the least expensive facilities are available. By not hanging up and terminating the call, the user indicates that the call is to proceed and the PBX system completes the call on the DDD trunk.
Even with the introduction of the distinctive warning tone to indicate selection of a DDD trunk, PBX customers are noticing that many PBX users ignore the warning tone or are unaware of the purpose of the warning tone to utilize DDD trunks when, in reality, the calls can be placed at a different time when less expensive trunks are available. Additionally, because the warning tone is so often ignored, the least expensive facilities are under-utilized at certain periods of the day.
There is a need, therefore, for methods and a system to limit access to the expensive trunks and to encourage users to utilize the least expensive trunking facilities.